1. Field
The present invention relates to computer aided design (CAD) and the analysis of models constructed in CAD software packages.
2. Description of the Related Art
Computer Aided Engineering (CAE), the use of computer software for the purpose of modeling and simulating the behavior of products in order to improve their quality, has become nearly ubiquitous in the manufacturing industry. Areas covered by CAE include but are not limited to stress and thermal analysis, fluid dynamics and kinematics.
Most CAE analysis systems are based on geometrical data stored in various 3D CAD formats. Examples of such formats are open standards like IGES (Initial Graphics Exchange Specification) or STEP (International Standard for Product Data Exchange) and proprietary formats like Pro Engineer, ACIS or Parasolid. After reading geometrical data stored in one such format, analysis software converts it to its internal representation. Thereafter, information may be set by the user for modeling purposes. This information may include boundary conditions (which are known values in the model such as intake and exit conditions, physical load, pressure conditions etc) and material properties. A computational mesh is usually generated. User input, together with mesh generation, are sometimes referred to as pre-processing. The mesh, together with the additional information set by the user is then sent to Solver software that uses numerical methods like the Finite Element Method to solve underlying algorithms in the model and thus perform the analysis. Finally, the results are visualized using Visualization software.
In recent years the analyzed models have become more and more complex. To tackle this complexity, the Solver software, which is generally the most resource and time consuming part of the analysis, has been offloaded to a cloud environment. The cloud can be viewed as remote, networked computing functionality, often sold as a service and usually arranged as servers on the internet. It can be much more powerful/fast than a user terminal. By using the resources made available in the cloud, it has become possible to perform analyses much larger than those possible on the client machine and in a much shorter time. Moreover, the move to a cloud model has made possible a much more efficient use of the resources, both hardware and software, available to a CAD modeling organization. The general layout of such a system is shown in FIG. 1.
In FIG. 1, a schematic diagram illustrates CAD/CAE tasks and their division between a client machine 10 and the cloud 20 according to the prior art. In the prior art, a 3D CAD model 30 is available on the client machine and used to set boundary conditions 40 and for mesh generation 50. The solver software 60 uses numerical methods for analysis and is provided on the cloud. The results are then returned to client machine 10 and visualized 70.
However, with the models continuing to increase in complexity, operations like setting boundary conditions are also becoming difficult for the client machine to handle. Indeed, just importing the 3D CAD data corresponding to a model of a current laptop or a server can take from tens of minutes to hours on a powerful workstation and the manipulation of such a model requires a powerful processor and graphic card.
Some operations can be performed using a “light-weight geometry format” also referred to as a “visualization format”. This is a simpler model than the full CAD model. Often, the main distinction between a CAD model and a “light-weight geometry format” is that the CAD model contains the full (continuous) analytical description of the model while the “light-weight geometry format” contains a discretized version of it.
Good candidates for visualization formats are those that store only the boundary of the geometry in a faceted form, like the STL format, VRML format, JT format or similar.
Setting analysis information like boundary conditions using a light-weight geometry format is possible, but made difficult by the fact that an accurate mesh can only be generated starting from the full 3D CAD data. Hence, there is a need to map the assigned information from the light-weight geometry format to the full 3D CAD data used for mesh generation.
The current generation of CAE systems uses the original larger 3D data to create the computational mesh. Based on this original data, they dynamically generate geometry in the light-weight visualization format and use it for the interaction with the user. Hence, for these prior art CAE systems, the mapping of information from the visualization format to the original 3D CAD geometry is straightforward, since the former was directly created from the latter and both are available to the application.
However, in many circumstances (such as when the CAD model has been converted to an open format) the CAD geometry from which the visualization file is generated is not the same as the CAD model currently in use.
CAE analysis tools found in the prior art can be split into two categories:    1. Boundary conditions and/or other settings are added to the mesh    2. Settings are added to the CAD model
In the first category, the CAD model is used to generate a high resolution mesh (with a resolution good enough for analysis). Then settings are added to this mesh, hence CAD data is not needed for adding settings. However, in this scenario, the mesh needs to be accurate (very high resolution) which means the computer carrying out pre-processing needs to have a very large memory and a powerful CPU to be able to read it.
In the second category, (corresponding to FIG. 1) the software tool can open a CAD model and settings are added by selecting the relevant points/edges/faces from the model. In general, a light-weight mesh is internally generated for visualization purposes (i.e., triangulation for 3D rendering) and this is actually what is being seen by the user. The computational mesh is generated after this process and the mapping between the selected CAD entities and the corresponding mesh entities is automatically made. Here, however, this is possible only because the software has all the required information at its disposal. Again, in this case the computer used for pre-processing needs to be powerful enough to be able to handle complex CAD models.
It is desirable to allow boundary conditions and other conditions to be set on a user computer, even when the user computer does not have the computing functionality to access a full CAD model. Moreover, it is desirable to be able to map CAE settings such as boundary conditions from the kind of visualization data which can be accessed on the less powerful local computer to a full CAD model on a more powerful computer which can perform analysis, even if visualization data on the local computer has not been directly derived from the CAD model which is used for analysis on the more powerful computer.